And I'm Audie Cornish. The government in Kiev accused the Kremlin today of trying to start another world war. This comes as a team of unarmed military observers in Ukraine is said to have been detained by pro-Moscow militants. The group is made up of representatives from several European countries. They've been monitoring growing tensions in eastern Ukraine.

Other observers, though, have had more success visiting occupied buildings and checkpoints. NPR's Soraya Sarhaddi Nelson is in eastern Ukraine and sent this report.

SORAYA SARHADDI NELSON BYLINE: The Ukrainian government, in recent days, announced the military operation in eastern Ukraine to clear out what they call terrorists. But here in Slavyansk, one of the key cities being targeted, there is little sign of any incursion. The many civilian checkpoints and posters proclaiming independence suggests the city remains under the control of pro-Russian separatists, but they are nowhere to be seen around the occupied government building,

In the adjacent square, children happily zoom around on miniature ATVs while their friends on bicycles give chase. Adult residents smile as they stroll past on this beautiful spring day, but the mood is somber at the nearby Lenin monument where a handful of mourners gather in front of the latest photo of a dead pro-Russian separatist to be taped to the statue's base.

The photo is of 22-year-old Sasha Lubenesk(ph) who friends say was fatally shot yesterday morning as he headed home after a shift at a nearby checkpoint. They blame a pro-Kiev sniper for the attack. Tears stream down the face of a dead guard's widow who was comforted by a stranger. Another mourner is Natalia Polchenko(ph).

NATALIA POLCHENKO: (Through interpreter) People are just dying for nothing. They were standing for truth.

BYLINE: She says she worries her son and grandson who also man checkpoints will share a similar fate. A short drive away, the supervisor of the checkpoint where the dead separatist stood guard says their barricade was overrun by the Ukrainian military shortly after Lubenesk was killed.

URI DEJENKO: (Speaking foreign language)

BYLINE: Uri Dejenko(ph) says 100 Ukrainian soldiers in six armored vehicles were too many for his 20 men to resist so they set fire to the barricade made up of dozens of tires and fled. New tires were already in place by the time independent monitors from the organization for security and cooperation in Europe showed up today to investigate.

One monitor is Lubo Mirakopi(ph) from Slovakia.

LUBO MIRAKOPI: We are one team that was sent today to Slavyansk. We monitor the situation in the city and at the barricades as well, and today our task is to check what is the situation at the barricades.